Principal Full Stack Engineer AI

About the Role We're partnering with a growing Sydney-based fintech building sophisticated data and technology products for global customers. The business is entering an important phase of growth, with a major re-architecture of its core platform underway and AI becoming increasingly embedded in both its products and engineering practices. They are looking for a senior hands-on engineer who can bring together strong software engineering, systems design, architecture and modern AI capability. This is not an MLOps, data science or pure machine learning role. The ideal person is an experienced backend or full-stack engineer who has developed strong architectural capability and has subsequently moved deeply into AI-enabled engineering. You'll work closely with the CTO and senior engineering team, helping shape the next generation of the platform while remaining close to the code. The role will suit someone who is comfortable moving between whiteboarding complex systems, making architectural decisions and building production software. Key Responsibilities Help design and re-architect a complex, data-intensive product platform.Define system boundaries, services and architectural patterns across the platform.Apply strong systems thinking to break complex business problems into scalable technical components.Design and build backend and full-stack product capabilities.Contribute to microservices and distributed systems architecture.Apply domain-driven design principles where appropriate.Help shape data flows, service interactions and core platform components.Remain hands-on with software development while contributing at an architectural level.Work closely with the CTO on significant technical and architectural decisions.Introduce AI and agentic capabilities into existing and new products.Help establish practical frameworks for building, evaluating and safely deploying AI-enabled software.Contribute to AI-native engineering practices, including the use of coding agents and modern development tooling.Ensure AI-enabled systems are supported by appropriate testing, evaluation, observability and guardrails.Whiteboard solutions and communicate technical decisions clearly to senior engineers and stakeholders.Influence engineering standards and help strengthen architectural capability across the wider team. Your Qualifications You are an experienced software engineer first, with strong architecture and systems design capability, and more recent hands-on experience working with AI. You will ideally bring: Significant experience as a backend or full-stack software engineer.Strong system design and software architecture capability.Experience designing microservices and distributed systems.Understanding of domain-driven design and service decomposition.Experience contributing to major platform re-architecture or modernisation initiatives.Strong hands-on coding capability.Experience building APIs and cloud-based applications.Ability to translate complex requirements into clear architectural concepts.Experience making architecture decisions while remaining close to implementation.Recent experience with Generative AI, agentic AI or LLM-enabled products.Experience taking AI-enabled systems beyond prototype stage and into production.Understanding of AI testing, evaluation, observability and guardrails.Strong technical communication and whiteboarding skills.Ability to influence experienced engineers without relying on formal authority. You may currently be working as a Principal Engineer, Staff Engineer, Tech Lead, Lead Engineer, Senior Full-Stack Engineer, Senior Backend Engineer or hands-on Software Architect. The strongest profile will be someone who built their career in software engineering and architecture, and has since moved meaningfully into AI. Why This Opportunity? This is an opportunity to join a growing fintech at a point where the technical decisions being made now will materially shape the next generation of its platform. You'll work directly with the CTO, contribute to a major re-architecture, and have genuine influence over how the engineering team designs systems, adopts AI and builds new product capabilities. The role offers the chance to stay highly hands-on while operating at a senior technical level, combining architecture, system design, coding and AI rather than moving away from engineering into people management. For someone who enjoys solving complex technical problems and wants to help define how AI is used in real production software, this is a role with significant scope and visibility.